Telemetry for intraunit railroad control



Dec. 2, 1969 J RAFF'EL ET AL 3,482,089

TELEMETRY FOR INTRAUNIT RAILROAD CONTROL Filed April 7. 1967 5 Sheets-Sheet 3 2602 6513 ms; 21:525.. m8 53 3. 560: xommmi ms; 2.; E ..zo.. mom 100 12 x00 6 wmummm m0 OOOM 5: a.

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LOOK FOR I'ONII 7 SINGLE SHOT PULSE LOOK FOR SHAPE "SYNC" 42 smeu: SHOT United States Patent O 3,482,089 TELEMETRY FOR INTRAUNIT RAILROAD CONTROL Jerome M. Raffel, Deer Valley Road, Highland, Md.

20777, and Robert R. Fontaine, 6015 Longfellow St., East Riverdale, Md. 20840 Filed Apr. 7, 1967, Ser. No. 629,233 Int. Cl. B611 27/04 US. Cl. 246182 18 Claims ABSTRACT OF THE DISCLOSURE A time division multiplex telemetry system for transmitting control signals between two or more locomotives connected together to form a consist. Each locomotive includes transmit and receive circuits and counter means for gating successive circuits to a transmit-receive bus which is connected through suitable means such as cables,

radio relays, or the like to the other locomotives in the consist.

FIELD OF THE INVENTION ted and synchronized operation of all the parts of the train.

DESCRIPTION OF THE PRIOR ART At the present time it is not unusual to connect two or more locomotives in tandem or in spaced locations along the length of a train to provide the power needed to pull the train efiiciently and at adequate speeds. When such an arrangement, and herein referred to as, a consist, is utilized, it becomes necessary to transmit control signals between the several locomotives to insure a common mode of operation. At the present time, the transmission of such control signals is carried out by way of individual wires connected between each control circuit of the lead locomotive and the corresponding control circuit in the trailing locomotives. This arrangement presently requires between 12 and 30 individual wires between the lead and trail locomotives, while proposed systems involving more sophisticated controls will require up to 121 wires. These connecting wires are carried by large, vulnerable and expensive jumper cables which not only present problems in reliability but, since these are special cables designed specifically for the systems, also present a problem of availability and supply. Invariably, when making up a consist, time is lost in trying to locate sufficient cables for the purpose for, since they are special cables, they cannot be made up on the spot from commonly available materials. Further, the large number of wires which must be connected multiply the problems caused by dirty contacts, improperly inserted connectors, broken wires and the like. An additional difficult found in the use of specially designed connecting cables of this type is that locomotives from different railroads may not use the same cable arrangement, thus making very difiicult the interconnection of such locomotives.

The failure rate of high wire content connector cables, due to physical failure of wires or connectors in the cables and to improper connection, the time lost in correcting or replacing such cables, plus the delays caused by nonavailability of the cables, can result in losses to a rail- 3,482,089 Patented Dec. 2, 1969 road amounting to thousands of dollars over the twentyyear life span of a diesel locomotive.

It will be apparent that many of the problems involved in the use of such cables can be reduced through periodic testing of the cables, better weather protection, better strain relief, and the like. Further, the use of coding would eliminate some wires, depending on the particular railroad and locomotive. That is, it would not be necessary to have a wire for forward, reverse and brake, for no two of these functions are operable at the same time. This would permit one wire to be eliminated. Similarly, the backup lights could be operated each time the reverse control is operated, thus shaving away another wire. This approach at reducing cable problems, at best, will only nibble at the problem, however, and will not provide a real solution.

SUMMARY OF THE INVENTION The present invention overcomes the problems and disadvantages of the prior art method of communication between the several locomotives of a consist by the application of a time multiplexed telemetering system. In general a system of this type involves the use of two stepping switches, one of each locomotive, the switches being interconnected so that they step in synchronism. The control circuit signal wires of each locomotive are connected to corresponding contacts of their respective stepping switches. Thus if a wire in the lead locomotive is energized by a control signal, and the switches in both the lead and trail units have selected the contact corresponding to that particular wire number, this signal will energize the same wire in the trailing locomotive. Each wire may be provided with a large capacitor to store the control signal for a complete cycle of the stepping switch; that is, until the switch has stepped through all of the wires and returned to the original point in preparation for repeating the process. Although mechanical stepping switch arrangements of this type are fairly common, they have a number of deficiencies; nevertheless, they are illustrative of the sampling and holding concepts from which the solid state electronic system of the present invention evolved. Thus, it is an object of the present invention to provide a communication system for a locomotive consist which utilizes an all solid state, electronic, time multiplexed telemetering system.

It is a further object of the present invention to provide a control system for a locomotive consist which utilizes a solid state electronic system involving time multiplexing concepts, but which does not disturb existing control systems and thus allows locomotives equipped with the system of the invention to be compatible with locomotives not so equipped.

Basically, the system of the present invention comprises a lead telemetry unit in one locomotive of a consist, the unit having a clock-driven counter mechanism which serves sequentially to gate each of a plurality of control circuits to a common output wire. The resulting output signal, which is a train of width-modulated command pulses, is transmitted to the trial telemetry units in the other locomotives in the consist either by way of a single connecting cable or by means of well-known radio communication techniques. The training unit receives the train of command pulses and these pulses are sequentially gated to the control circuits of the trailing locomotive by means of a counter circuit which is synchronized with the counter of the lead locomotive. Thus, each received command pulse is gated to its appropriate control circuit to activate the circuit in the manner determined by the corresponding lead locomotive control circuit, thereby causing the trial locomotive to function in conformity with the lead unit.

The invention contemplates that the telemetry unit of each locomotive will include both transmitting and receiving gates so that when it operates in either a lead mode or a trail mode it can both send and receive information. Each unit includes clock circuits and counters which can operate either to provide synchronizing signals in the lead mode or to respond to such signals from another source in the trail mode, whereby any given comotive can be connected to operate in a leading or trailing arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and additional features and advantages of the present invention will become apparent from a consideration of the following description of the invention, taken with the accompanying drawings in which:

FIG. 1 is a diagrammatic illustration of the basic principle on which the present invention is based;

FIG. 2 is a block diagram of a control system based on the principles of the illustration of FIG. 1, and constructed in accordance with the present invention;

FIGS. 3A-3E provide a graphical illustration of the wave forms utilized in the control system of the invention FIG. 3A showing the clock circuit output, FIG. 38 showing the timing of the synchronizing pulse from the counter, FIG. 3C illustrating a typical bus line wave train, FIG. 3D showing the relative durations of the various pulses of FIGS. 3A-3C, and FIG. 3D illustrating a typical dynamic braking signal; and

FIGS. 4A and 4B provide a detailed block diagram of the system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, there is illustrated a time multiplexed telemetering system in its simplest form. First and second locomotive telemetry units 40 and 40 are illustrated as being interconnected by three wires: a signal wire 42, a synchronizing wire 44 which carries a stepping signal, and a common, or return, wire 46, which provides the system ground. Telemetry unit 40 will be assumed to be in the lead locomotive here and in the following description, while locomotive telemetry unit 40' will be assumed to be located in a trailing unit or one of several trailing units. It will be apparent from the following description that the roles of these two units may be reversed by appropriate switching, since the circuitry in each unit will be identical.

As illustrated in FIG. 1, the telemetry unit 40 includes a mechanical stepping switch 50 of conventional construction having a drive mechanism comprised of a solenoid 52 and a movable armature 54. Stepping signals are applied to the solenoid by Way of line 56, periodically energizing the solenoid to step switch 50 from one contact to the next. The switch herein illustrated includes 32 contacts to accommodate the normal 27 signal wires presently in use in locomotive control circuits. The stepping signal applied to line 56 is also fed through connecting cable 44 to the solenoid 52' of stepping switch a in the telemetry unit 40' of the trailing locomotive. This connection insures that stepping switch 50 will sweep across its 32 contacts in synchronism with switch 50. If one of the control wires in the lead unit 40 is energized, the same wire in trailing unit 40 will be energized when the switches in both units reach that particular wire number. Each control wire is provided with a large capacitor, as at 58 and 58', to store the energizing voltage until the stepping switch has swept through all of the wires and reaches that particular wire. This is necessary if, for example, the stepping switch 50 is on wire number 2 when wire number 1 becomes energized, for there will be a lag in the transmission of that energizing Signal to the trailing unit while the switch steps through all the remaining contacts and returns to wire number 1. If the permitted lag time between the energization of a wire by a control signal, and the transmission of that control signal, is one second, and there are 32 steps, each step can last no longer than of a second. For this type of operation, the capacitor required to store'the control signal voltage would have to be at least 1000 f, quite a sizable capacitor to use in the quantities required for this type of system. Further, assuming that the switch could step at 32 steps per second, and that its rated life was one million steps, the operational life of the switch would be approximately 10 hours, an obviously unsatisfactorily short time. Because of these limitations, the time multiplexing approach has not previously been used in intraunit control of railroad locomotives.

The present invention overcomes the disadvantages inherent in stepping switch multiplexing, and thus makes possible a practical method of intraunit control using the principles described above by providing the solid state electronic system diagrammatically illustrated in FIG. 2, Considering now the telemetry unit 40 of the lead locomotive, it will be seen that the function of the stepping switch 50 of FIG. 1 is performed by a counter circuit 60, a decoder 62, transmitter gates 64 and receive gates 66. The counter is driven by an astable flip-flop clock circuit 68 which generates a train of spaced pulses having a predetermined, constant width. The clock pulses are applied to the counter by way of a selector wsitch 70 which permits the counter to be driven by clock circuit 68 when unit 40 is operating in the lead condition, but which permits the counter to be driven by clock pulses from another telemetry unit when unit 40 is operating in a trailing mode. Counter 60 may be a digital counter which provides a binary output progressing in steps from zero to 31 and which is then reset back to zero, and so on, as long as clock pulses are applied. These binary output signals are applied by way of cable 72 to the input of the decoder 62 which converts the binary signals to appropriate combinations of output pulses for sequentially activating the transmit and the receive gates 64 and 66 by Way of cables 74 and 76, respectively.

The values of the input command signals fed to the transmitter gates 64 are determined by the control signals appearing on the 27 locomotive control circuit signal wires. These command signals are in the form of on or off digital signals, and they ore transmitted in pulse form from the lead locomotive to the proper receiving gates in the trailing locomotives. As each of the transmitter gates are opened in sequence to the command signal inputs carried by cable 78, the corresponding command signal appears on output line 80, the sequence of command signals appearing in the form of a pulse-width modulated train. This train of output signals is applied through suitable output circuitry 82 and through an isolation diode '84 to the transmit-receive bus 42. Alternatively, this train of output signals could be applied to a radio transmitter for broadcast in a known manner.

In order to provide synchronization between the lead and trail units, the counter 60 is arranged to provide a synchronization pulse on line 86 every time the counter reaches the number 31. This synchronization pulse is applied through selector switch 88 to the output circuitry 82 for transmittal to the trailing units. This synchronization pulse causes all the counters in the trail units to reset to zero and insures that they will all register the same number as the lead unit counter after the first cycle following turn-on.

The command signals on line 42 are fed to the trailing unit 40 and pass through cables 90' and 92 to the receive gates 66'. These command pulses are also fed through line 94 and selector switch 70 to drive counter 60 in synchronism with the counter circuitry of the lead locoto permit the command signals from cable 92' to pass through their corresponding gates. These signals are then amplified by driver circuits 96 and fed through cable 98' to the respective locomotive control circuit signal wires in the trail locomotive which correspond to the circuits that originally produced them. Each line driver circuit is designed to hold its corresponding control signal for at least the period of time required for that signal to activate the corresponding locomotive control circuits.

It will be noted that the transmit gate circuits described with respect to the lead unit 40 are duplicated in the trail unit 40', with corresponding elements indicated by primed numbers. Similarly, the receive circuitry described with respect to the trail unit 40' is duplicated in the lead unit 40, with duplicate circuits being indicated by similar numbers. The positions of the selector switches 70, 70, 8'8 and 88 determine the mode of operation of the respective telemetry units and permit easy transfer of the system from one mode to the other. Thus, if the locomotive carrying unit 40' should be made the lead locomotive, it would only be necessary to switch these selector switches to the indicated modes to reverse the functions of the units. As noted in the drawing, the transmit-receive bus 42 need not be limited to a connection between two locomotives, but may be connected to any desired number of locomotives or other railroad cars in the train. It should also be noted that the present system eliminates the stepping signal cable 44 which was utilized in the embodiment of FIG. 1, the provision of clock circuits in each of the units and the generation of synchronizing signals by the counter circuits eliminating the need for this particular connector.

The pulse trains generated by the present telemetry system are shown in FIG. 3, pulse train A illustrating the output of the clock circuit 68 when unit 40 is in the lead mode. As shown, this clock circuit produces a train of evenly spaced, equal-width, constant amplitude pulses which continue as long as the clock circuit is operating. The synchronization pulse produced by counter 60 is illustrated in graph B. This pulse corresponds to zero time output from the clock and immediately follows the 31 output of the counter. It will be noted that the sync pulse is approximately three times as long as a time clock pulse so that it may be clearly distinguished by the receiving circuitry. Graph C of FIG. 3 illustrates the pulse train which appears on the transmit-receive bus line 42. This pulse train is a combination of the sync pulse and the output pulses from the various gate circuits. As has been noted, the locomotive control signals are on/otf signals which serve to modulate the width of the signals provided by the transmitter gates. Thus, where the control signal is off, the resultant pulse is approximately the same width as a clock pulse. However, when the control signal is on the output from the transmitter gate will be approximately double the width of a clock pulse. The relative widths of the various pulses are illustrated in FIG. 3, graph D, wherein the clock pulses are shown as lasting for 750 sec., the on pulses in the output train are shown as lasting 1500 ,uSEC. and the synchronizing pulses are shown as lasting 2250 p.566. The pulse shown in graph C as the output command signal for wire number 1 is an o signal, and thus will serve to advance the counter in the trail unit and cause wire number 1 in the control circuit of the trail locomotive to be off. A 1500 sec. command pulse such as is shown for wire number 4 is an on signal, and will advance the counter in the trail unit and will cause the corresponding control wire to be energized. The 2500 sec. pulse, which is added to pulse train C in the output circuit 82, is the sync pulse, which will reset counter 60' to zero. It should be noted that the wire numbers used in this system do not relate to any specific locomotive control system, the numbering being arbitrarily selected for purposes of illustration.

FIG. 4 of the drawings is a more detailed showing of a telemetry unit which may be installed in a locomotive.

Selected for purposes of illustration is the unit 40, shown in FIG. 2 as being mounted on the lead locomotive, and thus having the various selector switches arranged to provide a lead mode of operation. Even while operating in the lead mode, however, the telemetry unit must have a means for receiving information from the trailing locomotives, for the usual locomotive control circuits provide for this function. Thus, although most of the lead locomotive control circuits provide command signals, certain of these control circuits must be adapted for receiving information from trailing units. On the other hand, these same command circuits change to receiving circuits when the mode of operation is reversed, while the original receiving circuits are converted to transmitting circuits for sending data to the new lead unit. It is immaterial to the invention how many of the control circuits in the lead unit are set aside for receiving information from the trail unit, the particular number depending on the control functions being utilized in the system. Thus, the signal wires carrying information from the lead unit to a trailing unit are assigned wires numbers 1 to N and the signals from the trailing unit to the lead unit are carried on wires N +1 through 27.

The inputs from the 27 signal wires of the locomotive control circuit are connected to a terminal strip F, the terminals of which are numbered Fl through F27. The terminals on strip F are interconnected with predetermined contacts on a terminal strip G associated with the telemetry unit 40. These interconnections may be direct 1 to l, 2 to 2, etc., connections, or may be arranged in any desired order to permit a matching of functions between different control circuits in ditferent locomotives.

Each of the contacts on terminal strip G is connected through an RC filter to the input of a corresponding transmit gate 1 through 27, respectively. Thus, contact 1 is connected through an RC filter to transmit gate 1, contact 2 is connected through an RC filter to transmit gate 2, and so on. An exception to this order of connection is the terminal which carries the dynamic braking voltage for the locomotives. Since this function is not represented by a simple on-off signal, a different arrangement is required, and this arrangement is illustrated with the assumption that terminal G9 carries the dynamic braking signal. Contact 1 of terminal strip G is connected through RC network and line 102 to one of the four inputs of transmit gate 1. The RC network is used to suppress transients which may appear on the input lines. Similarly, terminal G2 is connected through RC network 104 and line 106 to one of the four inputs of transmit gate 2; terminal G3 is connected through its RC filter to transmit gate 3; terminal GN is connected through its RC filter to transmit gate N; and terminal G27 is'connected through its RC filter to transmit gate 27. Each of the transmit gates is comprised of an AND circuit of conventional construction, which, when selected, produces an output pulse the width of which is dependent upon the value of the input signal. Thus, if the control signal appearing on line 102 is otf when transmit gate 1 is selected, or opened, the signal on output line 108 will be the pulse indicated for wire number 1 in the pulse train waveform of FIG. 3C. In the same manner, if the input to transmit gate 4 is on when gate 4 is selected, the output from this gate appearing on line 110 will be similar to that illustrated in pulse train C of FIG. 3 for wire 7 70 to the driving input of counter 60, stepping it from zero to 31 and then shifting it back to zero, thus providing a binary combination of outputs in the known manner. The 0, 2 and 4 binary outputs of the register are applied through lines 112, 114, and 116, respectively, to a partial 7 decoder 118, while the 8 and 16 outputs are applied through lines 120 and 122, respectively, to a partial decoder 124. The number 31 count from register 60 is applied through line 126 to a synchronization signal generator 128 which responds to the signal on line 126 to produce a single output pulse of the shape illustrated in FIG. 3B, which pulse is fed through selector switch 88 and line 130 to the output circuitry to be described. The sync signal generator 128 is a single-shot pulse generator of conventional structure which produces a single square wave pulse in respons to an input signal.

The partial decoders 118 and 124 are each comprised of a plurality of three-input AND circuits, each of these circuits producing an output signal when certain predetermined input signal conditions are met. Partial decoder 118 includes 8 of these AND circuits, the output of each circuit being connected to a different one of the illustrated decoder outputs. The first of these AND circuits has its output connected to the decoder output labeled 0, 8, 16, 24, and produces its output signal only when the combination of binary coded signals on lines 112, 114 and 116 represent a 0, 8, 16 or 24 count in the register 60; that is, when there is a zero condition on each of the lines 1'12, 114 and 116. Similarly, the second AND circuit in the partial decoder 118 is connected to the decoder output labeled 1, 9, 17 and 25 and produces an output signal on that line only when the combination of binary inputs on lines 112, 114 and 116 correspond to a register count of 1, 9, 17 or 25. Thus, the second AND circuit only produces an output signal when line 112 carries a 1 signal and lines 114 and 116 carry signals. The eight AND circuits in decoder 118 sequentially activate the decoder outputs as the counter progresses from 0 to 7, and

repeats the cycle as the counter progresses from 8 to 15, from 16 to 23, and from 24 to 30.

During the 0 to 7 count on register 60, partial decoder 124 produces an output signal on its output line labeled 0-7, the AND circuit connected to the 0-7 output of this decoder responding to 0 inputs on lines 120 and 122 and a 1 input on line 132. The signal on line 132 is obtained from a single-shot pulse generator 134 which produces a 1, or on, signal in response to each pulse of the clock circuit 68. When the 8 count is reached on register 60, a l is produced on line 120 while the 0 remains on line 122. This deactivates the 0-7 output of decoder 124 and activates the AND circuit which produces a signal on the output line labeled 8-15. This signal remains until the register reaches count 16, at which time the decoder labeled 16-23 is activated. In this manner, each count of the register shifts the outputs of the decoders to select consecutive output lines, each combination of digital inputs to the decoders producing signals on a unique combination of decoder output lines.

The output lines from each of the partial decoders 118 and 124 are connect d to the transmit gates which correspond to the labels on the decoder output lines. Thus, for example, the output 0-7 of decoder 124 is connected through line 136 to one of the inputs of each of transmit gates l-7, as illustrated, there being no zero gate since this time period is used for producing the sync signal. Similarly, the output lab led 8-15 is connected through line 138 to an input on each of the transmit gates 8-15, etc. The output of partial decoder 118 which is labeled 1, 9, 17, is connected through line 1.40 to an input on each of the corresponding transmit gates l, 9, 17 and 25. Each of the other decoder outputs are similarly connected to the indicated transmit gates. By this manner of connection, each of the transmit gates is uniquely selected in sequence and is activated once in each cycle of counter 60.

Since each of the transmit gates 1 through are solid state active circuits, the final input to these circuits is a B+ voltage supplied through a selector switch 142 to either input line 144, feeding transmit gates 1 through N when the system is in the lead mode, or to line 146, feeding transmit gates N +1 through 30 when unit 40 is in the trailing mode. Three inputs are required for each AND transmit gate before an output pulse can be produced, and the width of this pulse is determined by the type of signal being applied to the remaining input from terminal strip G.

Returning now to a consideration of the dynamic brak ing signal which appears on terminal G9, it will be noted that this signal ditfers from the remaining locomotive control signals in that it is continuous, rather than digital, in form. This signal varies in amplitude with the amount of dynamic braking, and must be converted to a digital form before it can be utilized with this system. This conversion is accomplished by feeding the signal on terminal 9 to an analog-to-digital converter 150, which takes the variable amplitude dynamic braking signal and converts it to digital form, producing a binary combination of 0 and 1 signals on outputs 28, 29 and 30 of converter which is representative of the instantaneous analog amplitude. These digital signals are then applied in the normal manner to corresponding transmit gates 28, 29 and 30 to be transmitted upon selection of these gates. It will be noted that the output from converter 150 will only be transmitted when telemetry unit 40 is in its trail mode, for this is the only time that the B+ supply is connected to permit transmit gates 28, 29 and 30 to be activated.

The synchronization signal appearing on line 130 and the pulses appearing in sequence in the output lines of transmit gates 1 through N when unit 40 is in the lead mode and N+1 through 30 when in the trail mode are all applied to corresponding inputs of a 31 input OR gate 152. Gate 152 produces an output pulse corresponding to each input, and thus serves to convert the parallel inputs to a series pulse train output such as that illustrated in FIG. 3C. This series pulse train is amplified in a line driver 154 and is applied to the transmit-receive bus 42 for transmission to the trailing locomotive units.

Transmittal of the command information from the lead locomotive to the trail unit has 'been completed by the time that counter'60 has activated transmit gate N. Thereafter, until count 31 is reached, the lead unit is in a condition to receive information from the trail units by way of bus 42. Such received signals are applied to a pulse shaper and are then fed to two detector units which respond to the width of the received pulses to produce corresponding output pulses. The first detector is a singleshot pulse generator 162 which is designed to produce an output signal on line 164 only when the signal applied thereto from pulse shaper 160 is approximately 1900 sec. in duration; that is, it looks for and only responds to synchronization signals. An AND circuit 166 responds to the concurrent outputs of pulse shaper 160 and sync detector 162 to produce a pulse whenever a sync pulse is present. The output of AND circuit 166 serves to energize the B+ supply of the receive gates of unit 40 in a manner to be described, operating in this manner with each sync pulse to insure that the receive gates do not function before synchronization has been attained.

The output from pulse shaper 160 is also applied to an AND circuit 168 and to a single-shot pulse generator 170 which looks for and responds only to pulses of approximately 1100 ,usec. duration; that is, it responds to 011" pulses carried by bus 42. The output of AND circuit 168 is applied through line 172 to one input of each 30 receive gates. These receive gates correspond to gates 66 described with respect to FIG. 2, and each gate corresponds to one of the above-described transmit gates 1 through 30. These receive gates are selected in the same manner and by the same decoder circuitry as was the case for the transmit gates; thus they are uniquely selected by the combined outputs of partial decoders 118 and 124. In this manner the receive gates are opened by the counter 60 in synchronization with the opening of the transmit gates.

Although the incoming signals on bus 42 are not received until the N+1 transmit and receive gates are selected, it will be seen that these signals are applied by way of line 172 to all the receive gates 1 through in parallel. To permit operation of the proper receive gates, the B+ supply voltage is applied through mode selector switch 174 to lead line 176 and thus to each of the N+1 through 30 gates. The on signals applied through line 172 are fed to all of the receive gates, but since only the proper numbered gate will be opened during the period of time that each pulse in the incoming train is applied, the pulses will be accepted only by the proper receive gates and fed to their appropriate locomotive control circuit signal wires. The output of each receive gate drives an integration and holding circuit such as the circuit 180 connected to the output of receive gate 27. The circuit is designed to operate as a staircase generator, and thus requires that a minimum of two successive pulses be obtained before producing an output pulse on line 182. This output is amplified by a line driver 184 and conducted by line 186 to the corresponding terminal G27. Line 186 is connected directly to terminal G27, and bypasses the filter circuit associated with the terminal. The line driver is a power transistor which is capable of handling the heaviest relay found on a diesel locomotive. Diode arc suppressors may be included as an added safeguard against inductive kick from the locomotive relays.

The input signal received through line 172 by receive gates 28, 29 and 30 are the digital signals representing the amplitude of the dynamic braking signal from the trailing units. These signals, after passing through the integrating, holding, and line driver circuits provided for each of the receiving gates, are applied to corresponding inputs on a digital to analog converter 190. Converter 190 reconstitutes the dynamic braking signal into a variable amplitude analog form and feeds it through line 192 to the braking terminal 9 on terminal strip G. An example of the form which a dynamic braking signal might make is illustrated in FIG. 3E, wherein the analog signal representing the actual dynamic braking is illustrated as a smooth curve of variable amplitude, while the digital representation thereof is shown as a step voltage.

From the foregoing it will be seen that when the locomotive telemetry unit is in the lead mode, it will be transmitting command signals by way of wires 1 through N, and transmit gates 1 through N will be allowed to operate. Transmit gates N +1 through 30 will be deenergized by selector switch 142 during this mode. Receive gates 1 through N will, in this mode, be deenergized by selector switch 174, while receive gates N +1 through 30 will be sequentially energized to receive data from the trailing units.

If the telemetry unit 4.0 is to be used in the trailing mode instead of the lead mode, the reversal of function will be accomplished by changing each of the selector switches to the trail position. The changing of switch 70 disconnects clock circuit 68 from the counter 60, and connects the counter to the output of pulse shaper 160 by way of line 194. Switch 142 disconnects the B+ supply from transmit gates 1 through N and connects it to transmit gates N-l-l through 30, while selector switch 174 disconnects the B+ supply from receive gates N +1 through 30 and connects it to the receive gates 1 through N. This places the operation of telemetry unit 40 under the control of a remote unit. The first synchronization pulse which is received from the remote unit on line 42 is applied through pulse shaper 160 and sync detector 162 to provide a synchronization pulse on line 196 at the output of AND circuit 166. The sync pulse on line 196 is fed through selector switch 198 to the reset input 200 on counter 60, causing counter to reset to zero for synchronization with the remote units. The sync signal on line 196 is also applied to a delay circuit 202 which produces an output on line 204 which turns on the B-lsupply for the receive gates. Until this signal appears on line 204, none of the receive gates 1 through N can be activated, and this arrangement prevents input signals from pulse shaper 160 from affecting any of the receiver gates before synchronization is attained. It should be noted that delay circuit 202 responds to synchronization signals from the sync generator 128 (in lead mode) as Well as to sync signals applied through bus 42 from remote units to turn on the B+ supply for the receive gates. The signal on line 204 may operate a suitable relay for turning on the B+ supply.

When the unit 40 is operating in the trail mode, each input received on line 42, after passing through pulse shaper 160, is applied to line 194 and thus to the input of counter 62 to advance the counter one step. Thus, after synchronization, the counter 60 is stepped by the pulses produced in the remote unit and thus maintains the unit 40 in synchronization therewith. Counter 60 then sequences the transmit and receive gates 1 through 30 in the abovedescribed manner, with received data signals being applied through selected receive gates 1 through N to the appropriate terminals on terminal strip G. When count N +1 is reached, unit 40 then begins to transmit information by way of transmit gates N +1 through 30, while receive gates N +1 through 30 are disabled. Thus, for example, the information carried by the first received pulse following the synchronization pulse shifts the counter to select receive gate 1. If this first pulse is an off signal, AND gates 168 will not conduct, and receive gate 1 will not produce an output. However, if this pulse represents an on condition, AND gate 168 will conduct and receive gate 1 will be activated to produce an output data signal which will be fed through the integrate and hold circuit 206, line driver 208 and line 210- to terminal G1. In a similar manner, succeeding on pulses are fed through their corresponding receive gates to the appropriate locomotive control circuit signal wires to provide the required data, and the N +1 to 30 transmit gates provide output signals in their turn.

The timing of the present telemetry system was derived from a study of the relays found on locomotives. The combined mechanical-electrical time constants for such relays ranges from ms. to 600 ms.; thus the time lag of this system would have to be less than the existing worst case of 600 ms. If operation of a relay in the locomotive is desired within 0.'2 second of the time when the command signal is first given, and two signal pulses are required for pull-in of a relay to preclude the chance of a stray pulse causing such an action, then the system would have to count to 32 in 100 ms., disregarding the 0.6 relay pull-in time. This requirement dictates that the clock circuit produce a pulse every 3.1 ms., thus the illustrated clock circuit operates at 333 c.p.s., as seen in the waveforms of FIG. 3.

The transmit-receive bus from one locomotive can be directly connected with the transmit-receive bus from another locomotive by using a simple extension cord with some form of keyed plug. This greatly reduces the supply problem for jumper cables by eliminating the special set of wire cables now needed and replacing them with a very standard type of cable. A secure radio link could also be used so as to completely eliminate the requirement of a jumper cable. This radio link would be protected by the use of low transmitted power, directive antennas, coded addresses and code toning to avoid the interference from childrens walkie-talkies, taxicab radios, etc. If desired, the unit can be provided with both radio link and extension cord coupling capabilities;

It will be observed that the system, being digital, will expand in capacity by multiples of 2, but such an expansion in capacity does not necessarily increase the size, complexity or cost of the unit by the same factor. The above-described system handles 31 channels, but by adding one more stage to the telemetry, 63 channels could be provided. Of course, not all of the channels would have to be utilized. Inasmuch as no mechanical gates are involved in the operation of this system, but only solid state components are used, the system is capable of running at megacycle speeds, and the entire process, as described, could be speeded up considerably, if necessary.

The problem of interconnecting locomotives of different railroads is greatly alleviated with this system. The wires connecting terminal strips F and G can easily be switched around by a railroad electrician in accordance with a predetermined connection sequence to provide compatibility between virtually any combination of locomotives.

Although the present invention has been described in terms of a particular embodiment, many variations and modifications will be apparent to those skilled in the art, which variations will fall Within the spirit and scope of the invention as defined in the following claims.

We claim:

1. A telemetry system for relaying information between first and second stations, said first station including a first plurality of control units capable of producing and receiving control signals; a first telemetry unit comprising a plurality of transmit gates and a plurality of receive gates; means for connecting each said control unit to a corresponding transmit gate and a corresponding receive gate; an output bus; selector means for activating corresponding transmit and receive gates sequentially and in synchronism whereby said control units may be connected to said output bus in time sequence for transmitting or receiving control signals.

2. The telemetry system of claim 1, further including 3 switching means for transferring said telemetry unit between a lead mode and a trail mode, whereby predetermined ones of said control units are connected through corresponding transmit gates to said output bus and said output bus is connected to the remainder of said control units through corresponding receive gates.

3. The telemetry unit of claim 2, wherein said plurality of transmit gates and said plurality of receive gates each includes a lead mode group and a trail mode group, said switching means energizing said lead mode group of transmit gates and said lead mode group of receive gates to transfer said telemetry unit to the lead mode, and energizing said trail mode group of receive gates and said trail mode group of transmit gates to transfer said telemetry unit to the trail mode.

4. The telemetry unit of claim 3, wherein the receive gates which correspond to the transmit gates in the lead mode group form the trail mode group of receive gates, and wherein the receive gates which correspond to the transmit gates in the trail mode group form the lead mode group of receive gates.

5. The telemetry unit of claim 3, wherein said selector means activates first said lead transmit gates and then said "lead receive gates sequentially in said lead mode,

while in said trail mode said selector means sequentially activates first said trail receive gates and then said trail transmit gates.

6. The telemetry unit of claim 1, wherein said selector means comprises a counter having a unique output for each of said transmit gates and its corresponding receive gate, said telemetry unit further including switching means for transferring said telemetry unit between a lead mode and a trail mode whereby either a transmit gate or a receive gate, but not both, is activated for each unique counter output.

7. The telemetry unit of claim 6, wherein each of said transmit and receive gates comprises a logic circuit having a plurality of input connections and a single output connection, the input connections to each transmit logic circuit including a connection to said selected means, a connection to a corresponding control unit and a connection to said switching means, said output connections being connected to said output bus.

8. The telemetry unit of claim 7, wherein the plurality of input connections to each receive logic circuit includes a connection to said selector means, a connection to said switching means, and a connection to said output bus, the output connection of each receive logic circuit being connected to a corresponding control circuit.

9. In a time division multiplex telemetry system for transmitting control signals between first and second locomotives connected in a train, first and second telemetry units in said first and second locomotive, respectively, each telemetry unit including a plurality of lead transmit and trail transmit circuits, and a plurality of trail receive and lead receive circuits; each said locomotive including a plurality of control units adapted to produce and receive control signals, predetermined ones of said control units in each said locomotive being connected to corresponding lead transmit and trail receive circuits in the respective telemetry unit, the remaining control units in each said locomotive being connected to corresponding trail transmit and lead receive circuits; switching means for operating each locomotive in a lead mode or trail mode; an output bus for each said telemetry unit for establishing communication between said first and second telemetry units; and selector means for gating successive ones of said transmit and receive circuits in said telemetry units in synchronism, whereby control signals produced in control units at one locomotive can be received in corresponding control units at the other locomotive.

10. The telemetry system of claim 9, wherein said switching means for each locomotive energizes the lead transmit and the lead receive circuits of its respective telemetry unit to place said locomotive and its telemetry unit in the lead mode, and energizes the trail transmit and the trail receive circuits of its respective telemetry unit to place said locomotive and its telemetry unit in a trail mode, said first and second telemetry units being adapted to operate in opposite modes, whereby one of said locomotives leads and the other trails.

11. The telemetry system of claim 9, wherein said se lector means comprises clock-driven counter means for each said telemetry unit having a unique output for each of said transmit circuits and the corresponding receive gates, said switching means insuring that either a transmit gate or its corresponding receive gate, but not both, is activated in said telemetry unit for each unique output.

12. The telemetry system of claim 11, wherein said counter means for each telemetry unit produces a synchronizing pulse at the start of each counter cycle, the synchronizing pulse produced in said first telemetry unit being applied to said output buses when said first telemetry unit is in its lead mode, whereby said second telemetry unit when in a trail mode is synchronized with said first telemetry unit, said synchronizing pulse produced in said first telemetry unit being disconnected from said output buses when said first telemetry unit is in its trail mode, whereby said first telemetry unit may be synchronized with said second telemetry unit by a synchronizing pulse originating in said second telemetry unit.

13. The telemetry system of claim 12, wherein said counter means in said first telemetry unit is driven by clock pulses received on said output bus when said first telemetry unit is in its trail mode of operation.

14. The telemetry unit of claim 12, wherein each of said transmit and receive gates comprises a logical AND circuit, having a plurality of input connections and a single output connection, the input connections for each transmit AND circuit including a connection to said coun ter means, a connection to a corresponding control unit and a connection to said switching means, the output connection of each transmit AND circuit being to a logical OR circuit; the input connections for each receive AND circuit including a connection to said counter means, a connection to said switching means and a connection to said output bus, the output connection of each receive AND circuit being to a corresponding control unit.

15. The telemetry system of claim 9, wherein one of said control units carries analog information signals, said unit including analog to digital converter means for producing digital signals corresponding to the instantaneous value of said analog information signals, and means for feeding said digital signals to corresponding transmit gates.

16. The telemetry system of claim 15, further including digital to analog converter means for receiving from corresponding receive gates digital signals corresponding to an analog information signal and for reconstructing said analog information signal, and means for feeding said reconstructed analog information signal to said one of said control units.

17. The telemetry system of claim 16, wherein said analog information signal is a dynamic braking signal.

18. The telemetry unit of claim 9, wherein said means for connecting each said control unit to its corresponding receive gate comprises an integrate and hold circuit which 2,977,896 4/1961 Hammond 10561 2,980,036 4/1961 Puri-foy 10561 3,384,032 5/1968 Rufif 105-61 DRAYTON E. HOFFMAN, Primary Examiner US. Cl. X.R. 

